In general, a magnetic disk drive uses a magnetic disk (that is, a disk-shaped magnetic storage medium) as a storage medium. In the magnetic disk drive, data is written concentrically on the magnetic disk by a magnetic head. In a recent magnetic disk drive, the track pitch is made narrower to increase the recording density. In such a magnetic disk drive, even when the head (magnetic head) deviates a little from the target position of the target track on the disk (magnetic disk), the head gets closer to the boundary between the target track (hereinafter, referred to as a first track) and an adjacent track (hereinafter, referred to as a second track). When the head is close to the track boundary, there is a possibility that the head will read data from not only the first track but also the second track simultaneously. This phenomenon is known as inter-track interference (ITI).
In the magnetic disk drive, sequential reading typified by, for example, shingled reading occurs frequently. In sequential reading, data is read sequentially from consecutive tracks on the disk. Suppose data is read from the second track, followed by the reading of data from the first track in the sequential reading.
In the conventional art, second data read from the second track (more specifically, second data which has suffered no inter-track interference or from which inter-track interference has been cancelled) is stored in a buffer. According to the conventional art, even if first data read from the first track has suffered inter-track interference, the inter-track interference has been cancelled based on the second data in the buffer.
As described above, in the conventional art, to cancel inter-track interference, data on a track read earlier in sequential reading is stored in the buffer.
However, when data read from all the tracks in sequential reading is stored in the buffer, this leads to an increase in the storage capacity of the buffer. Therefore, the storage capacity of the buffer (more specifically, the capacity of a memory used as the buffer) is required to decrease, while realizing the cancellation of the inter-track interference.
In addition, the displacement (e.g., an unexpected displacement) of the head causing inter-track interference occurs even in sequential writing typified by shingled writing. In such a case, data on an adjacent track is overwritten. At this time, if data immediately before it was overwritten (already-written data) has been stored in the buffer, the already-written data is rewritten to an area where overwriting has occurred, thereby enabling the area to be restored to the state immediately before the overwriting occurred. For this reason, the buffer is necessary to realize rewriting resulting from an unexpected displacement of the head in sequential writing. Therefore, in sequential reading, too, the storage capacity of the buffer is required to decrease.